Method for producing metal porous body, and plating apparatus

ABSTRACT

A method for producing a metal porous body includes the steps of: performing electrical conduction treatment on a surface of a skeleton of a sheet-like resin porous body having the skeleton with a three-dimensional network structure, to obtain a conductive resin porous body having a conductive layer; performing electroplating treatment on a surface of a skeleton of the conductive resin porous body to obtain a plated resin porous body having a metal plating layer; and performing treatment of removing at least the resin porous body from the plated resin porous body to obtain a metal porous body. In the electroplating treatment, power is supplied to a rotation shaft of a rotating electrode roller while a contact surface of a power supply brush composed of a sintered body is brought into sliding contact with the rotation shaft, with a lubricant, not containing conductive metal powder, interposed therebetween.

TECHNICAL FIELD

The present invention relates to a method for producing a metal porous body and a plating apparatus.

This application claims priority on Japanese Patent Application No. 2017-240119 filed on Dec. 15, 2017, the entire contents of which are incorporated herein by reference.

BACKGROUND ART

Conventionally, a sheet-like metal porous body having a skeleton with a three-dimensional network structure has been used for various uses such as a filter that requires heat resistance, a battery electrode plate, a catalyst support, and a metal composite. As a method for producing the metal porous body, a method has been known in which, after the surface of the skeleton of a resin porous body is subjected to electrical conduction treatment, metal plating is performed by means of electroplating treatment and treatment of removing the resin porous body is performed, thereby obtaining a metal porous body (see, for example, PATENT LITERATURE 1).

In the method for producing the metal porous body described in PATENT LITERATURE 1, in performing the electroplating treatment, in order to form a metal plating layer on a single surface side or each surface side of a sheet-like resin porous body having a skeleton surface made conductive, electroplating treatment is repeatedly performed in a plurality of plating tanks while the resin porous body is being sequentially fed by feeding rollers and electrode rollers that serve as power supply cathodes outside the plating tanks. A current is sent to each electrode roller by bringing a rotation shaft of the electrode roller and a power supply brush into sliding contact with each other (see, for example, PATENT LITERATURE 2).

CITATION LIST Patent Literature

-   PATENT LITERATURE 1: Japanese Laid-Open Patent Publication No.     2015-153648 -   PATENT LITERATURE 2: Japanese Laid-Open Utility Model Publication     No. H5-97082 -   PATENT LITERATURE 3: Japanese Utility Model Registration No. 3075438 -   PATENT LITERATURE 4: Japanese Laid-Open Patent Publication No.     2001-157413 -   PATENT LITERATURE 5: Japanese Laid-Open Patent Publication No.     2011-205816 -   PATENT LITERATURE 6: Japanese Laid-Open Patent Publication No.     2001-346363 -   PATENT LITERATURE 7: Japanese Laid-Open Patent Publication No.     H6-84775

SUMMARY OF INVENTION

A method for producing a metal porous body according to the present disclosure is a method for producing a metal porous body, including the steps of: performing electrical conduction treatment on a surface of a skeleton of a sheet-like resin porous body having the skeleton with a three-dimensional network structure, to obtain a conductive resin porous body having a conductive layer; performing electroplating treatment on a surface of a skeleton of the conductive resin porous body to obtain a plated resin porous body having a metal plating layer; and performing treatment of removing at least the resin porous body from the plated resin porous body to obtain a metal porous body, wherein, in the electroplating treatment, power is supplied to a rotation shaft of a rotating electrode roller while a contact surface of a power supply brush composed of a sintered body is brought into sliding contact with the rotation shaft with a lubricant, not containing conductive metal powder, interposed therebetween.

“Not containing conductive metal powder” means to include not only the case where conductive metal powder is not contained at all but also the case where conductive metal powder is contained in a certain amount such that the advantageous effects of the present disclosure are achieved.

A plating apparatus according to the present disclosure is a plating apparatus for performing electroplating treatment on a surface of a skeleton of a conductive resin porous body obtained by forming a conductive layer on a surface of a skeleton of a sheet-like resin porous body having the skeleton with a three-dimensional network structure, to form a metal plating layer, the plating apparatus including: a plating tank; an electrode roller having a rotatable rotation shaft and configured to feed the conductive resin porous body to the plating tank by rotating the rotation shaft; and a power supply brush composed of a sintered body, wherein the power supply brush has a contact surface that is brought into sliding contact with the rotation shaft of the electrode roller with a lubricant, not containing conductive metal powder, interposed therebetween.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a metal porous body.

FIG. 2 is a schematic diagram showing a battery in which the metal porous body is used as a positive electrode plate.

FIG. 3 is a flowchart showing a method for producing a metal porous body according to an embodiment of the present invention.

FIG. 4A is an enlarged schematic view of the surface of a resin porous body.

FIG. 4B is an enlarged schematic view of the surface of a conductive resin porous body.

FIG. 4C is an enlarged schematic view of the surface of a plated resin porous body.

FIG. 4D is an enlarged schematic view of the surface of a metal porous body.

FIG. 5 is a side cross-sectional view showing an example of a plating apparatus.

FIG. 6 is a plan view showing a structure for supplying power to an electrode roller.

FIG. 7 is a cross-sectional view showing a power supply device.

FIG. 8A is a side view showing a power supply brush.

FIG. 8B is a diagram of the power supply brush as seen from the lower side of FIG. 8A.

FIG. 9 is a schematic diagram showing a modification of the plating apparatus.

DESCRIPTION OF EMBODIMENTS Technical Problem

In the case of performing electroplating treatment on a sheet-like resin porous body as in the above-described conventional art, it is necessary to apply a large current to each electrode roller, since the surface area of the resin porous body is large. Therefore, a sintered body containing copper or iron as a main component is generally used for a power supply brush for supplying power to each electrode roller.

However, the surface of the power supply brush for which a sintered body is used is porous, thus the frictional resistance between the power supply brush and the rotation shaft of the electrode roller increases, and jerkiness (rotational failure) easily occurs at the electrode roller that rotates at a low speed. When such jerkiness occurs, if the amount of plating on the resin porous body is small in the electroplating treatment, the plating thickness of a produced metal porous body is small, so that the skeleton of the metal porous body may be cracked thus reducing the strength, resulting in a decrease in the quality of the metal porous body.

Therefore, the present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a method for producing a metal porous body and a plating apparatus that can improve the quality of the metal porous body.

Advantageous Effects of Present Disclosure

According to the present disclosure, it is possible to improve the quality of the metal porous body.

DESCRIPTION OF EMBODIMENTS OF INVENTION

First, contents of embodiments of the present invention will be listed and described.

(1) A method for producing a metal porous body according to an embodiment of the present invention is a method for producing a metal porous body, including the steps of: performing electrical conduction treatment on a surface of a skeleton of a sheet-like resin porous body having the skeleton with a three-dimensional network structure, to obtain a conductive resin porous body having a conductive layer; performing electroplating treatment on a surface of a skeleton of the conductive resin porous body to obtain a plated resin porous body having a metal plating layer; and performing treatment of removing at least the resin porous body from the plated resin porous body to obtain a metal porous body, wherein, in the electroplating treatment, power is supplied to a rotation shaft of a rotating electrode roller while a contact surface of a power supply brush composed of a sintered body is brought into sliding contact with the rotation shaft with a lubricant, not containing conductive metal powder, interposed therebetween.

In the method for producing a metal porous body, in the electroplating treatment, the contact surface of the power supply brush composed of a sintered body is brought into sliding contact with the rotation shaft of the electrode roller with the lubricant interposed therebetween, and thus the frictional resistance between the power supply brush and the rotation shaft of the electrode roller can be reduced. Accordingly, even when the amount of plating is reduced in the electroplating treatment, occurrence of jerkiness at the rotation shaft of the electrode roller can be inhibited. As a result, occurrence of cracking, in the metal porous body, that reduces the strength of the metal porous body can be inhibited, and thus the quality of the metal porous body can be improved.

Generally, in the case of applying a fluid between components for the purpose of applying electricity thereto, a method in which a conductive material such as metal powder is mixed into the fluid to cause the fluid itself to have electrical conductivity, is adopted. However, in the case where conductive metal powder is contained in a lubricant that corresponds to the fluid, when the lubricant is used over a long period of time, the metal powder may be oxidized, resulting in significant deterioration of electrical conductivity. In addition, by the metal powder aggregating into lumps and accumulating between the contact surface of the power supply brush and the rotation shaft of the electrode roller, the contact area between the contact surface and the rotation shaft of the electrode roller may be decreased.

On the other hand, in the above (1), since the lubricant does not contain conductive metal powder, deterioration of electrical conductivity due to oxidization of metal powder can be prevented. In addition, since metal powder can be prevented from aggregating into lumps and accumulating between the contact surface of the power supply brush and the rotation shaft of the electrode roller, a decrease in the contact area between the contact surface and the rotation shaft of the electrode roller can be prevented, and the contact area that is stable can be ensured.

(2) In the electroplating treatment, heat generated in the power supply brush is preferably dissipated to the outside by a heat dissipation member connected to the power supply brush.

In this case, a rise in the temperature of the power supply brush composed of a sintered body can be effectively inhibited by the heat dissipation member, and thus corrosion of the sintered body due to a rise in the temperature of the power supply brush can be inhibited.

(3) In the electroplating treatment, abrasion powder generated on the contact surface of the power supply brush is preferably guided and discharged to the outside by a groove formed on the contact surface.

In this case, the abrasion powder can be inhibited from aggregating into lumps and accumulating between the contact surface of the power supply brush and the rotation shaft of the electrode roller. Thus, a decrease in the contact area between the contact surface and the rotation shaft of the electrode roller can be inhibited, and the contact area that is stable can be ensured.

(4) The groove is preferably formed so as to extend in a direction crossing a direction tangent to the rotation shaft of the electrode roller.

In this case, the abrasion powder can be efficiently guided and discharged to the outside by the groove, and thus the abrasion powder can be further inhibited from aggregating into lumps and accumulating between the contact surface of the power supply brush and the rotation shaft of the electrode roller.

(5) Preferably, in the electroplating treatment, the power supply brush is disposed at each of the rotation shafts provided at both axial end portions of the electrode roller, and power is supplied to each rotation shaft while the contact surface of the corresponding power supply brush is brought into sliding contact with the rotation shaft with the lubricant interposed therebetween.

In this case, when power is supplied from the power supply brush to the electrode roller, it is possible to adjust the current density to be in an appropriate range via the power supply brush, which is disposed at each of the rotation shafts provided at both axial end portions of the electrode roller.

(6) In the electroplating treatment, the power supply brush is preferably biased and pressed against the rotation shaft of the electrode roller by a biasing member.

In this case, the contact pressure between the contact surface of the power supply brush and the rotation shaft of the electrode roller can be increased by the biasing member.

In addition, since the contact pressure can be increased by the biasing member, also due to the power supply brush being composed of a sintered body and recesses and projections being formed on the surface of the power supply brush, even if the lubricant not containing conductive metal powder is used, a layer of the lubricant becomes partially thin (at a portion where each local projection of the power supply brush and the electrode roller are in contact with each other). Thus, even with the lubricant not containing conductive metal powder, flow of a current can be inhibited from being blocked. Therefore, in the above (6), more significant effects are achieved by using a sintered body as the power supply brush, increasing the contact pressure between the contact surface of the power supply brush and the rotation shaft of the electrode roller by the biasing member, and combining the use of the lubricant not containing conductive metal powder.

(7) In the electroplating treatment, when the electrode roller is rotated, a part of an outer circumference of the rotation shaft of the electrode roller is preferably immersed into the lubricant stored within a container that is disposed below the rotation shaft.

In this case, by rotating the electrode roller, the lubricant within the container can be applied to the entirety of the outer circumference of the rotation shaft. Thus, with a simple configuration, the contact surface of the power supply brush can be brought into sliding contact with the rotation shaft of the electrode roller with the lubricant interposed therebetween. In addition, since the container is disposed below the rotation shaft of the electrode roller, when abrasion powder generated on the contact surface of the power supply brush drops due to the weight thereof or the like, the dropping abrasion powder can be received within the container. Accordingly, the abrasion powder can be easily collected during maintenance work.

(8) A plating apparatus according to an embodiment of the present invention is a plating apparatus for performing electroplating treatment on a surface of a skeleton of a conductive resin porous body obtained by forming a conductive layer on a surface of a skeleton of a sheet-like resin porous body having the skeleton with a three-dimensional network structure, to form a metal plating layer, the plating apparatus including: a plating tank; an electrode roller having a rotatable rotation shaft and configured to feed the conductive resin porous body to the plating tank by rotating the rotation shaft; and a power supply brush composed of a sintered body, wherein the power supply brush has a contact surface that is brought into sliding contact with the rotation shaft of the electrode roller with a lubricant, not containing conductive metal powder, interposed therebetween.

In the plating apparatus, in the electroplating treatment, the contact surface of the power supply brush composed of a sintered body is brought into sliding contact with the rotation shaft of the electrode roller with the lubricant interposed therebetween, and thus the frictional resistance between the power supply brush and the rotation shaft of the electrode roller can be reduced. Accordingly, even when the amount of plating is reduced in the electroplating treatment, occurrence of jerkiness at the rotation shaft of the electrode roller can be inhibited. As a result, occurrence of cracking, in a metal porous body obtained after the electroplating treatment, that reduces the strength of the metal porous body can be inhibited, and thus the quality of the metal porous body can be improved.

Generally, in the case of applying a fluid between components for the purpose of applying electricity thereto, a method in which a conductive material such as metal powder is mixed into the fluid to cause the fluid itself to have electrical conductivity, is adopted. However, in the case where conductive metal powder is contained in a lubricant that corresponds to the fluid, when the lubricant is used over a long period of time, the metal powder may be oxidized, resulting in significant deterioration of electrical conductivity, and the metal powder may aggregate into lumps and accumulate between the contact surface of the power supply brush and the rotation shaft of the electrode roller, thereby decreasing the contact area between the contact surface and the rotation shaft of the electrode roller.

On the other hand, in the above (8), since the lubricant does not contain conductive metal powder, deterioration of electrical conductivity due to oxidization of metal powder can be prevented. In addition, since metal powder can be prevented from aggregating into lumps and accumulating between the contact surface of the power supply brush and the rotation shaft of the electrode roller, a decrease in the contact area between the contact surface and the rotation shaft of the electrode roller can be prevented, and the contact area that is stable can be ensured.

DETAILS OF EMBODIMENTS OF INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that at least parts of the embodiment described below may be combined as desired.

<Metal Porous Body>

FIG. 1 is a schematic diagram showing a metal porous body. The metal porous body 10 has a sheet-like appearance and has a skeleton 11 forming a three-dimensional network structure. A large number of pores defined by the three-dimensional network structure are formed so as to be arranged from the surface of the metal porous body 10 to the interior of the metal porous body 10.

The metal porous body 10 can be used, for example, as a positive electrode plate 21 of a battery 20 as shown in FIG. 2. That is, as shown in FIG. 2, the battery 20 in which the metal porous body 10 according to the present embodiment is used mainly includes the positive electrode plate 21, a separator 22, and a negative electrode plate 23 that are disposed within a casing 24. The positive electrode plate 21, the separator 22, and the negative electrode plate 23 are disposed within the casing 24 in a state of being layered. The layered body of the positive electrode plate 21, the separator 22, and the negative electrode plate 23 is held in a wound state. The positive electrode plate 21 includes the metal porous body 10 according to the present embodiment and an active material (not shown) with which the metal porous body 10 is filled.

<Production Process for Metal Porous Body>

FIG. 3 is a flowchart showing a method for producing the metal porous body 10 according to an embodiment of the present invention. Hereinafter, the flow of the entirety of the method for producing the metal porous body 10 will be described with reference to FIG. 3.

First, a sheet-like resin porous body that has a three-dimensional network structure and serves as a base is prepared (step ST1). FIG. 4A is an enlarged schematic view of the surface of a resin porous body 1 serving as a base. In the resin porous body 1, a large number of pores defined by a three-dimensional network structure are formed so as to be arranged from the surface of the resin porous body 1 to the interior of the resin porous body 1.

Next, electrical conduction treatment is performed on the surface of the skeleton of the resin porous body 1 (step ST2). By this step, a conductive resin porous body 3 having a conductive layer 2 formed by a thin electric conductor on the surface of the skeleton of the resin porous body 1 as shown in FIG. 4B can be obtained.

Subsequently, electroplating treatment is performed on the surface of the skeleton of the conductive resin porous body 3 (step ST3). By this step, a plated resin porous body 5 having a metal plating layer 4 formed on the surface of the skeleton of the conductive resin porous body 3 as shown in FIG. 4C can be obtained.

Next, treatment of removing the resin porous body 1, which is the base, from the plated resin porous body 5 is performed (step ST4). In this removing treatment, the resin porous body 1 is eliminated by burning or the like, whereby the metal porous body 10 in which only the metal plating layer 4 is left can be obtained (see FIG. 4D). Hereinafter, each step will be sequentially described in detail.

<Preparation of Resin Porous Body>

The sheet-like resin porous body 1 having the skeleton with the three-dimensional network structure is prepared. Examples of the material of the resin porous body 1 include a resin foam, a nonwoven fabric, felt, and a woven fabric, and these materials may be combined as necessary. In addition, the material of the resin porous body 1 is not particularly limited, but a material that can be eliminated by burning after the metal plating layer 4 is formed on the surface of the skeleton by the electroplating treatment is preferable.

The material of the resin porous body 1 is preferably a flexible material, since a sheet-like material is particularly easily broken due to handling thereof if the rigidity of the material is high. In the present embodiment, a resin foam is preferably used as the material of the resin porous body 1. The resin foam only needs to be porous, and a known or commercially-available one can be used. Examples of such a material include foamed urethane and foamed styrene. Among them, foamed urethane is particularly preferable from the viewpoint of having a high porosity. The thickness, the porosity, and the average pore size of the resin foam are not particularly limited in the present invention, and can be set as appropriate according to use.

The thickness of the resin foam in the present embodiment is, for example, 1.0 mm to 2.5 mm, preferably 1.0 mm to 1.6 mm, and more preferably 1.0 mm to 1.3 mm.

In addition, the average pore size of the resin foam in the present embodiment is, for example, 250 μm to 500 μm, preferably 300 μm to 450 μm, and more preferably 300 μm to 400 μm.

<Electrical Conduction Treatment>

Next, for performing electroplating treatment, electrical conduction treatment is performed in advance on the surface of the skeleton of the resin porous body 1. The method for the electrical conduction treatment is not particularly limited as long as the conductive layer 2 can be formed on the surface of the skeleton of the resin porous body 1. Examples of the material for forming the conductive layer 2 include metals such as nickel, titanium, and stainless steel, and carbon powder such as graphite and amorphous carbon including carbon black, etc. Among them, particularly, carbon powder is preferable, and carbon black is more preferable. The conductive layer 2 only needs to be continuously formed on the surface of the skeleton of the resin porous body 1. The weight of the conductive layer 2 per unit area is not particularly limited, and may be normally about 5 g/m² to about 15 g/m², and preferably about 7 g/m² to about 10 g/m².

As specific examples of the electrical conduction treatment, for example, in the case of using nickel, electroless plating treatment, sputtering treatment, and the like are preferable. In addition, in the case of using a material such as carbon black, graphite, or a metal such as titanium and stainless steel, treatment in which a mixture obtained by adding a binder to fine powder of the material is applied to the surface of the skeleton of the resin porous body 1 is preferable.

As the electroless plating treatment using nickel, for example, the resin porous body 1 may be immersed into a known electroless nickel plating bath such as a nickel sulfate aqueous solution containing sodium hypophosphite as a reducing agent. Before the immersion into the plating bath, the resin porous body 1 may be immersed as necessary into an activation liquid containing a very small amount of palladium ions (a cleaning liquid manufactured by JAPAN KANIGEN Co., Ltd.) or the like.

As the sputtering treatment using nickel, for example, the resin porous body 1 may be attached to a substrate holder, then a DC voltage may be applied between the substrate holder and a target (nickel) while inert gas is being introduced, whereby ionized inert gas may be collided against the nickel, and the blown nickel particles may be accumulated on the surface of the skeleton of the resin porous body 1.

<Electroplating Treatment>

When the thickness of the metal plating layer is increased by at least one of the above electroless plating treatment and the above sputtering treatment, it is not necessary to perform electroplating treatment. However, from the viewpoint of productivity and cost, a method is preferably adopted in which, as described above, first, electrical conduction treatment is performed on the resin porous body 1, and then the metal plating layer 4 is formed on the conductive resin porous body 3 by electroplating treatment.

The electroplating treatment only needs to be performed according to an ordinary method. For example, in the case of nickel plating, a known or commercially-available one can be used as a plating bath. Examples of the plating bath include a Watts bath, a chlorination bath, and a sulfamic acid bath. In the above electroless plating treatment or sputtering treatment, the conductive resin porous body 3 is immersed into the plating bath, the conductive resin porous body 3 and a counter electrode plate of a plating metal are connected to a cathode and an anode, respectively, and a DC or pulse interrupted current is applied thereto, whereby the metal plating layer 4 can be further formed on the conductive layer 2 of the conductive resin porous body 3. The metal plating layer 4 only needs to be formed on the conductive layer 2 such that the conductive layer 2 is not exposed (see FIG. 4C).

FIG. 5 is a side cross-sectional view showing an example of a plating apparatus 30 that continuously performs electroplating treatment on the sheet-like conductive resin porous body 3. The plating apparatus 30 of the present embodiment is configured to feed the sheet-like conductive resin porous body 3 from the left side to the right side in FIG. 5, and includes a first plating tank 31, a second plating tank 32 disposed at the downstream side of the first plating tank 31, and a power supply device 50 (see FIG. 7).

The first plating tank 31 includes a plating bath 33, a cylindrical electrode 34 (cylindrical cathode), and an anode 35 (cylindrical anode) provided on an inner wall of a container. By the conductive resin porous body 3 passing through the inside of the plating bath 33 along the cylindrical electrode 34, the metal plating layer 4 is formed on one surface side (the lower surface side in FIG. 5) of the conductive resin porous body 3.

The second plating tank 32 includes a plurality of tanks 36 for forming the metal plating layer 4 on the other surface side (the upper surface side in FIG. 5) of the conductive resin porous body 3. The conductive resin porous body 3 undergoes metal plating by being sequentially fed and passing through plating baths 39 in a state of being held between a plurality of feeding rollers 37 and a plurality of electrode rollers 38, which are disposed adjacent to the respective tanks 36. In each of the plurality of tanks 36, an anode 40 is provided at the other surface side of the conductive resin porous body 3 with the plating bath 39 interposed therebetween. By supplying power to the anodes 40 and rotation shafts 38 a of the electrode rollers 38 (tank-outer power supply cathodes), the metal plating layer 4 is formed on the other surface side of the conductive resin porous body 3.

FIG. 6 is a plan view showing a structure for supplying power to the rotation shafts 38 a of the electrode roller 38. The rotation shafts 38 a of the electrode roller 38 are provided at both axial end portions of the electrode roller 38 which rotates in contact with the sheet-like conductive resin porous body 3. Each of the rotation shafts 38 a of each electrode roller 38 is supplied with power by a plurality of power supply brushes 51 each of which is in sliding contact with the outer circumferential surface of the rotation shaft 38 a. Each power supply brush 51 is composed of, for example, a sintered body containing copper as a main component, such that a large current can be applied to the rotation shaft 38 a of the electrode roller 38. The “main component” refers to a component having a highest mass content, and impurities may be contained as long as the advantageous effects of the present embodiment are achieved.

Each of the rotation shafts 38 a of each electrode roller 38 is composed of a sintered body made of metal, and plating can be performed on the rotation shaft 38 a from the viewpoint of prevention of corrosion. Each power supply brush 51 may be composed of a sintered body containing a main component other than copper, such as iron.

Each power supply brush 51 is designed to be abraded against the rotation shaft 38 a of the electrode roller 38. The coefficient of dynamic friction of each power supply brush 51 is about 0.01 to 0.40 and preferably 0.10 to 0.30. This is because: when the coefficient of dynamic friction is less than these ranges, it is disadvantageous in cost; and when the coefficient of dynamic friction is greater than these ranges, the problem arises that the slidability is deteriorated and the amount of abrasion is increased.

FIG. 7 is a cross-sectional view showing the power supply device 50 including the plurality of power supply brushes 51. The power supply device 50 is provided at each of both axial end portions of the electrode roller 38. The power supply device 50 of the present embodiment includes the plurality of (in this example, two) power supply brushes 51, a plurality of biasing members 52 that press and bias the respective power supply brushes 51 against the outer circumferential surface of the rotation shaft 38 a of the electrode roller 38, and a casing 53.

The casing 53 is formed, for example, by a metal member having electric conductivity. The casing 53 of the present embodiment is formed in a rectangular cross-sectional shape so as to surround the rotation shaft 38 a of the electrode roller 38, and the biasing members 52 are attached to two surfaces, that is, the upper surface and the left surface, among four inner surfaces of the casing 53.

Each biasing member 52 is not particularly limited as long as the biasing member 52 presses and biases the power supply brush 51 against the outer circumferential surface of the rotation shaft 38 a of the electrode roller 38. For example, each biasing member 52 of the present embodiment is formed by a plate spring that is bent in an S cross-sectional shape. One end portion of each biasing member 52 is attached to the corresponding inner surface of the casing 53, for example, by a fixing plate 56A and a bolt 57A, and the power supply brush 51 is connected to the other end portion of each biasing member 52, for example, by a fixing plate 56B and a bolt 57B. Accordingly, contact surfaces 51 a (described later) of the two power supply brushes 51 are pressed against the outer circumferential surface of the rotation shaft 38 a of the electrode roller 38 from the upper side and the left side in FIG. 7 by the biasing force of the corresponding biasing members 52.

Each biasing member 52 is preferably formed by a metal member having both excellent electric conductivity and excellent heat dissipation. Each biasing member 52 of the present embodiment is formed by a metal member obtained by tinning copper having electric conductivity and having excellent heat dissipation. In addition, in the present embodiment, the fixing plates 56A and 56B also have heat dissipation. Thus, the biasing member 52 and the fixing plates 56A and 56B serve as a heat dissipation member that dissipates heat generated in the power supply brush 51 connected to this biasing member 52, to the outside. The heat dissipation member connected to the power supply brush 51 may be formed by a member other than the biasing member 52 and the fixing plates 56A and 56B, or may be formed by the biasing member 52, the fixing plates 56A and 56B, and the casing 53.

In each power supply brush 51, a surface that faces the outer circumferential surface of the rotation shaft 38 a of the electrode roller 38 is the contact surface 51 a that is in sliding contact with the outer circumferential surface. The contact surface 51 a is formed in a circular arc shape along the outer circumferential surface of the rotation shaft 38 a of the electrode roller 38. In addition, a lubricant 58 not containing conductive metal powder is applied to the contact surface 51 a. “Not containing conductive metal powder” means to include not only the case where conductive metal powder is not contained at all but also the case where conductive metal powder is contained in a certain amount such that the advantageous effects of the present embodiment are achieved.

As the lubricant 58, a lubricating oil that is a liquid, or grease is used. In the present embodiment, liquid paraffin, which is a lubricating oil, is used as the lubricant 58. Here, paraffin is a type of hydrocarbon compound (organic compound), is a generic term for alkanes having 20 or more carbon atoms (chain saturated hydrocarbons having the general formula of C_(n)H_(2n+2)), and is considered synonymous for aliphatic saturated hydrocarbons C_(n)H_(2n+2) in some cases regardless of the number of carbon atoms. In addition, paraffin is a mixture of hydrocarbons obtained from petroleum or crude oil through processes such as distillation and refinement and is a colorless and transparent liquid. Liquid paraffin can be considered as a pure hydrocarbon since liquid paraffin is highly purified by removing impurities such as aromatic hydrocarbons and sulfur compounds contained in lube-oil distillate of petroleum that is a raw material.

In the present invention, the liquid paraffin is a mixture (weight-average molecular weight: 483) of hydrocarbons (the number of carbon atoms is about 15 to 20), and a reagent having a purity of about 95% equivalent to first class grade is preferably used. In addition, the density of the liquid paraffin is preferably not less than 0.855 g/ml, and is, for example, 0.87 g/ml in the present embodiment.

When a low viscosity is defined as being 40 cSt to 75 cSt, an intermediate viscosity is defined as being 75 cSt to 300 cSt, and a high viscosity is defined as being not less than 300 cSt, the viscosity of the liquid paraffin is preferably the low viscosity to the lower limit of the intermediate viscosity from the viewpoint of easy handling. In the present embodiment, the viscosity of the liquid paraffin is, for example, 75.8 cSt, and the kinetic viscosity of the liquid paraffin is, for example, 67.65 cSt (mm²/s at 40° C.).

The lubricant 58 is stored within a container 59 that is disposed on the lower surface within the casing 53 and below the rotation shaft 38 a of the electrode roller 38. An opening 59 a is formed at the upper side of the container 59. A part of the outer circumference of the rotation shaft 38 a of the electrode roller 38 is immersed in the lubricant 58 within the container 59 through the opening 59 a. Accordingly, by rotating the electrode roller 38, the lubricant 58 within the container 59 is applied to the entirety of the outer circumferential surface of the rotation shaft 38 a. Thus, each power supply brush 51 can supply power to the rotation shaft 38 a by bringing the contact surface 51 a of the power supply brush 51 into sliding contact with the outer circumferential surface of the rotation shaft 38 a with the lubricant 58 interposed therebetween. In addition, when abrasion powder generated on the contact surface 51 a of each power supply brush 51 drops due to the weight thereof or the like, the dropping abrasion powder can be received within the container 59 through the opening 59 a.

FIG. 8A is a side view showing the power supply brush 51. In addition, FIG. 8B is a diagram of the power supply brush 51 as seen from the lower side in FIG. 8A. As shown in FIG. 8A and FIG. 8B, a plurality of (in this example, three) slit-shaped grooves 55 are formed on the contact surface 51 a of the power supply brush 51. These grooves 55 are formed on the contact surface 51 a at regular intervals in the longitudinal direction of the contact surface 51 a (the right-left direction in FIG. 8A and FIG. 8).

Each groove 55 is formed so as to extend in a direction crossing a tangent direction T (see FIG. 8B) in which the contact surface 51 a of the power supply brush 51 is tangent to the rotation shaft 38 a of the electrode roller 38. In the present embodiment, each groove 55 is formed so as to extend linearly over the entirety of the contact surface 51 a in the lateral direction of the contact surface 51 a (the up-down direction in FIG. 8A and FIG. 8) in a state of being inclined at a predetermined angle (for example, 30°) relative to the lateral direction. Accordingly, abrasion powder generated on the contact surface 51 a of the power supply brush 51 due to sliding contact with the rotation shaft 38 a of the electrode roller 38 can be efficiently guided and discharged to the outside by the plurality of grooves 55.

The current density during supply of power from each power supply brush 51 to the rotation shaft 38 a of the electrode roller 38 (the ratio of the current to the total cross-sectional area of the power supply brush 51) is about 5 A/cm² to about 15 A/cm² and preferably 8 A/cm² to 13 A/cm². When the current density is less than these ranges, the size of the entire power supply device 50 is increased and the distance from the power supply device 50 to the corresponding tank 36 is lengthened, and thus voltage loss is increased. On the other hand, when the current density is greater than these ranges, the temperature of the power supply brush 51 rises, and thus it is necessary to ensure heat resistance of members around the power supply brush 51, which is disadvantageous in cost.

The weight of the metal plating layer 4 per unit area is not particularly limited, but is normally about 150 g/m² to about 400 g/m², and the sum of the weight of the conductive layer 2 per unit area and the weight of the metal plating layer 4 per unit area is preferably not less than 200 g/m² and not greater than 350 g/m². This is because: when the above sum is less than this range, the strength of the metal porous body may be reduced; and when the above sum is greater than this range, the power supply brush made of carbon has increased heat generation, or the amount of plating is increased, which is disadvantageous in cost.

The electroplating treatment is not limited to the electroplating treatment of the present embodiment, and, for example, a plating treatment method using a preliminary plating tank or a plating treatment method using a preliminary plating tank and a lift type main plating tank may be adopted.

FIG. 9 is a schematic diagram showing a modification of the plating apparatus 30. In the present modification, the plating apparatus 30 includes a preliminary plating tank 61 and a lift type main plating tank 62 disposed at the downstream side of the preliminary plating tank 61.

The preliminary plating tank 61 includes a plating bath 63, an anode 64 (cylindrical anode), a presser roller 65, and an electrode roller 66 having a rotation shaft 66 a (power supply cathode) at each end portion thereof. The conductive resin porous body 3 preliminarily undergoes plating on one side surface (the upper surface side in FIG. 9) of the conductive resin porous body 3 by being sequentially fed and passing through the inside of the plating bath 63 in a state of being held between the presser roller 65 and the electrode roller 66,

The main plating tank 62 includes a plating bath 67, a first presser roller 68, a first electrode roller 69 having a rotation shaft 69 a (power supply cathode) at each end portion thereof, a pair of first anodes 70 (cylindrical anodes), a first feeding roller 71, a second feeding roller 72, a pair of second anodes 73 (cylindrical anodes), a second presser roller 74, and a second electrode roller 75 having a rotation shaft 75 a (power supply cathode) at each end portion thereof.

In the main plating tank 62, the conductive resin porous body 3 is sequentially drawn in between the pair of first anodes 70 within the plating bath 67 in a state of being held between the first presser roller 68 and the first electrode roller 69. At this time, plating is performed on both surface sides of the conductive resin porous body 3 by supplying power to the rotation shafts 69 a of the first electrode roller 69 and the pair of first anodes 70.

Next, the conductive resin porous body 3 is sequentially fed between the pair of second anodes 73 by the first and second feeding rollers 71 and 72 within the plating bath 67. Then, the conductive resin porous body 3 is sequentially lifted from the inside of the plating bath 67 in a state of being held between the second presser roller 74 and the second electrode roller 75. At this time, plating is performed on both surface sides of the conductive resin porous body 3 by supplying power to the pair of second anodes 73 and the rotation shafts 75 a of the second electrode roller 75.

The rotation shafts 66 a of the electrode roller 66 of the preliminary plating tank 61 are supplied with power by power supply brushes (not shown) that are in sliding contact with the rotation shafts 66 a. Similarly, the rotation shafts 69 a and 75 a of the first and second electrode rollers 69 and 75 of the main plating tank 62 are supplied with power by power supply brushes (not shown) that are in sliding contact with the rotation shafts 69 a and the rotation shafts 75 a.

The power supply brushes that supply power to the rotation shafts 66 a, 69 a, and 75 a of the respective electrode rollers 66, 69, and 75 are formed similar to the above embodiment, and thus the description thereof is omitted.

<Treatment of Removing Resin Porous Body>

Treatment of removing the resin porous body 1 from the plated resin porous body 5 (see FIG. 4C) obtained by the electroplating treatment is performed. In this removing treatment, for example, the resin porous body 1 is removed from the plated resin porous body 5 in an acidic atmosphere such as atmospheric air at not lower than about 600° C. and not higher than 800° C. and preferably not lower than 600° C. and not higher than 700° C., and then heating is performed in a reductive atmosphere at 750° C. or higher (higher temperatures are desirable but the temperature is preferably 1000° C., since higher temperatures are disadvantageous in cost, or from the viewpoint of the material of the body of a reducing furnace). As reductive gas, hydrogen gas or a mixed gas of hydrogen and carbon dioxide or an inert gas can be used, or these gases can be also used in combination as necessary. In particular, it is preferred if hydrogen gas is always added to reductive gas, since the efficiency of redox is improved.

With the method for producing a metal porous body according to the present embodiment and the plating apparatus 50, in the electroplating treatment, the contact surface 51 a of each power supply brush 51, which is composed of a sintered body, is brought into sliding contact with the rotation shaft 38 a of the electrode roller 38 with the lubricant 58 interposed therebetween, and thus the frictional resistance between the power supply brush 51 and the rotation shaft 38 a of the electrode roller 38 can be reduced. Accordingly, even when the amount of plating is reduced in the electroplating treatment, occurrence of jerkiness at the rotation shafts 38 a of the electrode rollers 38 can be inhibited. As a result, occurrence of cracking, in the metal porous body 10, that reduces the strength of the metal porous body 10 can be inhibited, and thus the quality of the metal porous body 10 can be improved.

Generally, in the case of applying a fluid between components for the purpose of applying electricity thereto, a method in which a conductive material such as metal powder is mixed into the fluid to cause the fluid itself to have electrical conductivity, is adopted. However, in the case where conductive metal powder is contained in a lubricant that corresponds to the fluid, when the lubricant is used over a long period of time, the metal powder may be oxidized, resulting in significant deterioration of electrical conductivity, and the metal powder may aggregate into lumps and accumulate between the contact surface 51 a of the power supply brush 51 and the rotation shaft 38 a of the electrode roller 38, thereby decreasing the contact area between the contact surface 51 a and the rotation shaft 38 a of the electrode roller 38.

On the other hand, in the present embodiment, since the lubricant 58 does not contain conductive metal powder, deterioration of electrical conductivity due to oxidization of metal powder can be prevented. In addition, since metal powder can be prevented from aggregating into lumps and accumulating between the contact surface 51 a of the power supply brush 51 and the rotation shaft 38 a of the electrode roller 38, a decrease in the contact area between the contact surface 51 a and the rotation shaft 38 a of the electrode roller 38 can be prevented, and the contact area that is stable can be ensured.

In the electroplating treatment, heat generated in each power supply brush 51 can be dissipated to the outside by the biasing member 52 and the fixing plates 56A and 56B connected to the power supply brush 51. Accordingly, a rise in the temperature of the power supply brush 51 composed of a sintered body can be effectively inhibited, and thus corrosion of the sintered body due to a rise in the temperature of the power supply brush 51 can be inhibited.

In the electroplating treatment, abrasion powder generated on the contact surface 51 a of each power supply brush 51 can be guided and discharged to the outside by the grooves 55 formed on the contact surface 51 a. Accordingly, the abrasion powder can be inhibited from aggregating into lumps and accumulating between the contact surface 51 a of the power supply brush 51 and the rotation shaft 38 a of the electrode roller 38. Thus, a decrease in the contact area between the contact surface 51 a and the rotation shaft 38 a of the electrode roller 38 can be inhibited, and the contact area that is stable can be ensured.

Since each groove 55 is formed so as to extend in the direction crossing the tangent direction T in which the contact surface 51 a of the power supply brush 51 is tangent to the rotation shaft 38 a of the electrode roller 38, the abrasion powder can be efficiently guided and discharged to the outside by the groove 55. Accordingly, the abrasion powder can be further inhibited from aggregating into lumps and accumulating between the contact surface 51 a of the power supply brush 51 and the rotation shaft 38 a of the electrode roller 38.

The power supply brushes 51 are disposed at the respective rotation shafts 38 a provided at both axial end portions of the electrode roller 38, and power is supplied to each rotation shaft 38 a, in the electroplating treatment, while the contact surfaces 51 a of the corresponding power supply brushes 51 are brought into sliding contact with the rotation shaft 38 a with the lubricant 58 interposed therebetween. Accordingly, at the time of supply of power, it is possible to adjust the current density to be in an appropriate range via the power supply brushes 51, which are disposed at the respective rotation shafts 38 a provided at both axial end portions of the electrode roller 38.

In the electroplating treatment, since each power supply brush 51 is biased and pressed against the rotation shaft 38 a of the electrode roller 38 by the biasing member 52, the contact pressure between the contact surface 51 a of the power supply brush 51 and the rotation shaft 38 a of the electrode roller 38 can be increased.

In addition, since the contact pressure can be increased by the biasing member 52, also due to each power supply brush 51 being composed of a sintered body and recesses and projections being formed on the surface of the power supply brush 51, even if the lubricant 58 not containing conductive metal powder is used, a layer of the lubricant 58 becomes partially thin (at a portion where each local projection of the power supply brush 51 and the electrode roller 38 are in contact with each other). Thus, even with the lubricant 58 not containing conductive metal powder, flow of a current can be inhibited from being blocked. Therefore, in the present embodiment, more significant effects are achieved by using a sintered body as each power supply brush, increasing the contact pressure between the contact surface of the power supply brush 51 and the rotation shaft 38 a of the electrode roller 38 by the biasing member 52, and combining the use of the lubricant 58 not containing conductive metal powder.

By rotating each electrode roller 38 a, the lubricant 58 within the container 59 can be applied to the entirety of the outer circumferential surface of the rotation shaft 38 a. Thus, with a simple configuration, the contact surface 51 a of each power supply brush 51 can be brought into sliding contact with the rotation shaft 38 a of the electrode roller 38 with the lubricant 58 interposed therebetween. In addition, since the container 59 is disposed below the rotation shaft 38 a of the electrode roller 38, when abrasion powder generated on the contact surface 51 a of the power supply brush 51 drops due to the weight thereof or the like, the dropping abrasion powder can be received within the container 59 through the opening 59 a. Accordingly, the abrasion powder can be easily collected during maintenance work.

[Others]

Although the method for producing a metal porous body according to the above embodiment has been described for the case of application to a method for producing a metal porous body that is used as an electrode of a battery, the use of the metal porous body is not necessarily limited to an electrode of a battery, and the method may be applied to a method for producing a metal porous body that is used as a filter, a catalyst support, a metal composite, or the like that requires heat resistance. However, it is particularly effective to apply the method for producing a metal porous body according to the above embodiment to a method for producing a metal porous body that is used as an electrode of a battery.

It should be noted that the embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the scope of the claims rather than by the meaning described above, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

REFERENCE SIGNS LIST

-   -   1 resin porous body     -   2 conductive layer     -   3 conductive resin porous body     -   4 metal plating layer     -   5 plated resin porous body     -   10 metal porous body     -   11 skeleton     -   20 battery     -   21 positive electrode plate     -   22 separator     -   23 negative electrode plate     -   24 casing     -   30 plating apparatus     -   31 first plating tank     -   32 second plating tank     -   33 plating bath     -   34 cylindrical electrode     -   35 anode     -   36 tank     -   37 feeding roller     -   38 electrode roller     -   38 a rotation shaft     -   39 plating bath     -   40 anode     -   50 power supply device     -   51 power supply brush     -   51 a contact surface     -   52 biasing member (heat dissipation member)     -   53 casing     -   55 groove     -   56A, 56B fixing plate (heat dissipation member)     -   57A, 57B bolt     -   58 lubricant     -   59 container     -   59 a opening     -   61 preliminary plating tank     -   62 main plating tank     -   63 plating bath     -   64 anode     -   65 presser roller     -   66 electrode roller     -   66 a rotation shaft     -   67 plating bath     -   68 first presser roller     -   69 first electrode roller     -   69 a rotation shaft     -   70 first anode     -   71 first feeding roller     -   72 second feeding roller     -   73 second anode     -   74 second presser roller     -   75 second electrode roller     -   75 a rotation shaft     -   T tangent direction 

1: A method for producing a metal porous body, comprising the steps of: performing electrical conduction treatment on a surface of a skeleton of a sheet-like resin porous body having the skeleton with a three-dimensional network structure, to obtain a conductive resin porous body having a conductive layer; performing electroplating treatment on a surface of a skeleton of the conductive resin porous body to obtain a plated resin porous body having a metal plating layer; and performing treatment of removing at least the resin porous body from the plated resin porous body to obtain a metal porous body, wherein in the electroplating treatment, power is supplied to a rotation shaft of a rotating electrode roller while a contact surface of a power supply brush composed of a sintered body is brought into sliding contact with the rotation shaft with a lubricant, not containing conductive metal powder, interposed therebetween. 2: The method for producing a metal porous body according to claim 1, wherein, in the electroplating treatment, heat generated in the power supply brush is dissipated to the outside by a heat dissipation member connected to the power supply brush. 3: The method for producing a metal porous body according to claim 1, wherein, in the electroplating treatment, abrasion powder generated on the contact surface of the power supply brush is guided and discharged to the outside by a groove formed on the contact surface. 4: The method for producing a metal porous body according to claim 3, wherein the groove is formed so as to extend in a direction crossing a direction tangent to the rotation shaft of the electrode roller. 5: The method for producing a metal porous body according to claim 1, wherein, in the electroplating treatment, the power supply brush is disposed at each of the rotation shafts provided at both axial end portions of the electrode roller, and power is supplied to each rotation shaft while the contact surface of the corresponding power supply brush is brought into sliding contact with the rotation shaft with the lubricant interposed therebetween. 6: The method for producing a metal porous body according to claim 1, wherein, in the electroplating treatment, the power supply brush is biased and pressed against the rotation shaft of the electrode roller by a biasing member. 7: The method for producing a metal porous body according to claim 1, wherein, in the electroplating treatment, when the electrode roller is rotated, a part of an outer circumference of the rotation shaft of the electrode roller is immersed into the lubricant stored within a container that is disposed below the rotation shaft. 8: A plating apparatus for performing electroplating treatment on a surface of a skeleton of a conductive resin porous body obtained by forming a conductive layer on a surface of a skeleton of a sheet-like resin porous body having the skeleton with a three-dimensional network structure, to form a metal plating layer, the plating apparatus comprising: a plating tank; an electrode roller having a rotatable rotation shaft and configured to feed the conductive resin porous body to the plating tank by rotating the rotation shaft; and a power supply brush composed of a sintered body, wherein the power supply brush has a contact surface that is brought into sliding contact with the rotation shaft of the electrode roller with a lubricant, not containing conductive metal powder, interposed therebetween. 